In view of the harsh working conditions of diesel engine cylinder liner, the inner surface of CrMoCu alloy cast iron cylinder liner sample was compositely treated by ion carbonitrided/sulfurized process, 0.5 μm FeS particles were added to the lubricating oil with the proportion of 1% to 4%, and the influence of the amount of FeS particles on the wear resistance of composite modified layer was investigated under the test load of 300 N. The tribological properties of the synergistic effect of composite modified layer and FeS particle lubricating oil were investigated under the load range of 20 N to 300 N, and the interaction mechanism was discussed. The results show that the prepared composite modified layer is mainly composed of Fe₃N, Fe₂C, FeS and FeS₂ phases, and the hardness is 1.6 times higher than that of matrix. The optimal addition of FeS particles is 2.5%, the FeS particles added to the lubricating oil can be continuously adsorbed on the friction pair surface, which forms the adsorbed  layer and then plays a solid lubrication role. It supplements the thin thickness of sulfurized layer and the insufficiency of a single lubrication method. The porous structure of sulfurized layer is conducive to the adsorption, oil storage and molecular diffusion of FeS particles. The oxide, sulfide, phosphate and other boundary films generated by the tribochemical reaction improve the anti-friction and anti-wear ability of sample surface. The high-hardness carbonitrided layer can provide effective support for the sulfurized layer, lubricating oil film, boundary film and adsorption layer, and prolong its anti-wear effect time. The number of FeS particles adsorbed and retained on the surface of friction pair is less under light load，the synergistic effect of composite modified layer and lubricating oil containing FeS particles is not obvious. The synergistic effect is excellent under 300 N, which improves the wear resistance of cylinder liner sample surface by 53.1% and the wear resistance of ring specimen surface by 49.9%.